Semiconductor device fabrication involves many processes including wire bonding processes, in which electrical connections are formed between a semiconductor die (e.g. an integrated circuit die) and a substrate (e.g. a lead frame) to which the semiconductor die is bonded. In conventional wire bonding processes, a free air ball is first formed at one end of a wire before bonding the free air ball to the semiconductor die via ball bonding. Another wire bond (e.g. a wedge bond) is then formed between the wire and the substrate (e.g. a lead frame) to form an electrical connection between the semiconductor die and the substrate. Thereafter, the wire is clamped before being pulled in a direction away from substrate to detach the wire at the location of the wedge bond.
A non-stick-on-lead (‘NSOL’) bonding failure occurs if the wire is not properly bonded to the substrate via the wedge bond. In the case of conductive semiconductor dies, NSOL bonding failure can be detected via an electrical circuit as shown in FIG. 1. After a wire 100 from a wire spool (not shown) is detached from an electrical connection between a semiconductor die 106 and a substrate 104 at a location of a wedge bond 102, a tail wire 105 will be formed together with an open electrical circuit between the tail wire 105 and the substrate 104. As the tail wire 105 is at a higher relative electrical potential than the substrate 104 (which is grounded), detection of the higher electrical potential of the tail wire 105 relative to the conductive semiconductor die 106 means that the wire 100 has been successfully detached from the wedge bond 102, and accordingly, that NSOL bonding failure has not occurred. However, if the wire 100 is not successfully detached from the wedge bond 102 due to bonding failure of the wedge bond 102, the electrical potential of the wire 100 would be at an electrical potential that is comparable to the electrical ground potential of the substrate 104, because the semiconductor die 106 (to which the wire 100 is connected) is conductive. Therefore, detection of the lower electrical potential of the tail wire 105 relative to the conductive semiconductor die 106 means that NSOL bonding failure had occurred during wire bonding.
However, the aforesaid method of detecting NSOL bonding failure is applicable only to conductive semiconductor dies and not to non-conductive semiconductor dies. Therefore, it is an object of the present invention to seek to provide methods of detecting bonding failure that applies, particularly but not exclusively, to non-conductive semiconductor dies, and/or to provide the general public with a useful choice.